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49-YEAR-OLD WOMAN WITH PAIN IN THE LEFT ARM
SOURCE REVISION
xxxxxx-xxxxxx-SK 161121
MAIN LEARNING POINTS
1-Systematic, detailed EKG interpretation
2-Posterior STEMI; leads V7-V9
INTRODUCTION
”A 49-year-old woman presents to Emergency Department with pain in the left arm. How to you interpret her EKG?” (Show EKG-1 then EKG-2)
DISCUSSION
Overhead Coronary Anatomy
Lateral STEMI is usually caused by occlusion of the proximal circumflex artery. The patient’s “dominant” coronary artery is that one that supplies the posterior descending artery (usually the left).
Overhead Posterior STEMI-1
A posterior myocardial infarction affects the posterio-inferior wall of the left ventricle. A posterior infarction is usually caused by pathology in the distal circumflex artery. Findings that suggest a posterior infarction on the 12 lead EKG are:
• A large R wave in V1-V3
• ST depression in V1-V3
• An upright T wave in V2
Overhead Posterior STEMI-2
The best way to diagnose or exclude a posterior STEMI is through the use of posterior electrodes (V7-V9)
Course
The patient received acetylsalicylic acid (320 mg) and Clopidogrel 600 mg in the ED. Coronary angiography revealed a severely stenosed proximal Cx and an occlusion a couple of cm distally. PCI to the Cx.
REFERENCES
Morris F, Brady WJ. Acute myocardial infarction-Part I. BMJ 2002;324:831-4
49-YEAR-OLD WOMAN WITH PAIN IN THE LEFT ARM
DETAILED EKG-INTERPRETATION
|O |Rate |Around 75 beats/min |
| |Rhythm |Sinus |
|P |P wave |No evidence of right or left atrial hypertrophy |
| |PR segment |Normal PR duration (< 0.2 sec) |
|Q |Q wave |No pathological Q waves |
| |QRS complex |Normal QRS width (< 0.12 sec) |
|R |Axis |Normal (positive in I & positive in II) |
| |R-wave |No evidence of right or left ventricular hypertrophy |
|S |S-wave |No evidence of right or left ventricular hypertrophy |
| |ST segment |ST elevation in aVL; ST depression inferior and anteroseptal leads |
|T |T wave |Flat T wave in aVL; no T wave inversion in the anteroseptal leads |
| |QTc time |< 480 msec |
HYPOTHESIS
□ Lateral +/- posterior STEMI
QUESTIONS
How does one best determine whether a posterior STEMI is present?
□ V7-V9 leads
What does the EKG with V7-V9 leads (EKG-2) show?
□ ST elevation in V7-V8
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